The evolution of the microbial spoilage population for air- and vacuum-packaged meat (beef and pork) stored at 4°C was investigated over 11 days. We monitored the viable counts (mesophilic total aerobic bacteria, Pseudomonas spp., Enterobacteriaceae, lactic acid bacteria, and Enterococcus spp.) by the microbiological standard technique and by measuring the emission of volatile organic compounds (VOCs) with the recently developed proton transfer reaction mass spectrometry system. Storage time, packaging type, and meat type had statistically significant (P < 0.05) effects on the development of the bacterial numbers. The concentrations of many of the measured VOCs, e.g., sulfur compounds, largely increased over the storage time. We also observed a large difference in the emissions between vacuum- and air-packaged meat. We found statistically significant strong correlations (up to 99%) between some of the VOCs and the bacterial contamination. The concentrations of these VOCs increased linearly with the bacterial numbers. This study is a first step toward replacing the time-consuming plate counting by fast headspace air measurements, where the bacterial spoilage can be determined within minutes instead of days.

In this paper, we report the results of treating commercial samples of pork meat with ozone in order to determine whether such treatment reduces microbial growth and hence extends the shelf lifetime of such products. The technique of Proton-Transfer-Reaction Mass Spectrometry (PTR-MS) was used to study volatile emissions with the signal detected at mass 63 (assumed to be a measure for dimethylsulphide) being used as a diagnostic of bacterial activity. Such a signal was found to strongly increase with time for an untreated meat sample whereas ozone-treated meat samples showed much reduced emissions—suggesting that the microbial activity had been greatly suppressed by ozone treatment. An independent analysis, however, revealed that microbial counts were very high, independent of the treatment.

We have developed an objective method for the determination of a herb extract's quality based on headspace measurements by proton-transfer-reaction mass spectrometry (PTR-MS); this quality was checked by a sensory analysis until now. This novel method enables the company ‘Bionorica’ to ensure that they are only selling high-quality products and therefore avoid complaints of the customer. The method could be also used for controlling and optimising the production process.

The potential of proton transfer reaction mass spectrometry (PTR-MS) as a tool for classification of milk fats was evaluated in relation to quality and authentication issues. Butters and butter oils were subjected to heat and off-flavouring treatments in order to create sensorially defective samples. The effect of the treatments was evaluated by means of PTR-MS analysis, sensory analysis and classical chemical analysis. Subsequently, partial least square-discriminant analysis models (PLS-DA) were fitted to predict the matrix (butter/butter oil) and the sensory grades of the samples from their PTR-MS data. Using a 10-fold cross-validation scheme, 84% of the samples were successfully classified into butter and butter oil classes. Regarding sensory quality, 89% of the samples were correctly classified. As the milk fats were fairly successfully classified by the combination of PTR-MS and PLS-DA, this combination seems a promising approach with potential applications in quality control and control of regulations.

In this paper we report an investigation of the effects of E/N over the range of 90–140 Td on the product ions resulting from the reactions of H3O+ with 12 saturated alcohols using a proton transfer reaction mass spectrometer (PTR-MS). The alcohols included in this study are methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol, 2-butanol, cyclopentanol, 1-pentanol, cyclohexanol, and 1-hexanol. Only in the cases of methanol and ethanol are any substantial amounts of the protonated parent observed at any E/N. For the other saturated alcohols predominantly fragment ions are observed. This implies that attempts to identify and hence monitor saturated alcohols in trace concentrations in a complex chemical environment using PTR-MS will be fraught with difficulties because a given m/z will not be unique to a particular chemical compound, i.e., multiple species could be present at a given m/z. In addition to changes in E/N we present preliminary results with regards to changing the conditions in the generation of the reagent ions via altering the operational conditions within the ion source (a hollow cathode). We present product ion branching ratios as a function of hollow cathode emission current for cyclohexanol, 1-propanol and 2-propanol at fixed E/N. Although not part of the reaction chamber, we have found that changing the hollow cathode emission current results in modifications to the product ion branching ratios. We presume that these observed changes are a result of altering the internal energies of the reagent ions and thereby modify the reaction kinetics and dynamics occurring within the drift tube of a PTR-MS.